This invention relates to dyes, to inks and to their use in ink jet printing (xe2x80x9cIJPxe2x80x9d).
IJP is a non-impact printing technique in which droplets of ink are ejected through a fine nozzle onto a substrate without bringing the nozzle into contact with the substrate.
There are many demanding performance requirements for dyes and inks used in IJP. For example they desirably provide sharp, non-feathered images having good water-fastness, light-fastness and optical density. The inks are often required to dry quickly when applied to a substrate to prevent smudging, but they should not form a crust over the tip of an ink jet nozzle because this will stop the printer from working. The inks should also be stable to storage over time without decomposing or forming a precipitate which could block the fine nozzle.
According to a first aspect of the present invention there is provided a mono-azo compound of Formula (1) and salts thereof: 
wherein:
D is the residue of a mono-azo chromophore;
Z is an optionally substituted nitrogen containing heterocyclic group;
R1 is H or optionally substituted alkyl;
the dyes of Formula (1) being free from fibre reactive groups;
provided that the compound of Formula (1) is other than the compound of Formula (A): 
R1 is preferably H or optionally substituted C1-4-alkyl, more preferably H or C1-4-alkyl optionally substituted by hydroxy, carboxy, sulpho or cyano. Examples include methyl, ethyl, n-propyl, iso-propyl, hydroxyethyl, cyanoethyl, sulphopropyl and carboxyethyl. It is especially preferred that R1 is H.
The nitrogen containing heterocyclic group represented by Z is preferably attached to the triazine ring in Formula (1) by a bond to a nitrogen atom in the heterocyclic group.
Z may contain more than one nitrogen atom. Z may also contain other heteroatoms in addition to nitrogen, for example one or more sulphur or oxygen atom(s).
Z may be a monocyclic or polycyclic nitrogen containing heterocyclic group which may be saturated, unsaturated or aromatic. It is preferred however that Z is a bicyclic or, more preferably, a monocyclic nitrogen containing heterocyclic group. It is especially preferred that Z is a 6 or more especially a 5 membered monocyclic nitrogen containing heterocyclic group.
Preferably Z is free from primary and secondary amino groups because we have found that the presence of such groups reduces the light-fastness of the compounds of Formula (1).
Preferred groups represented by Z include morpholino, pyrrolyl, imidazolyl, isoindolyl, indazolyl, pyrazolyl, pyrrolidinyl, pyrrolinyl, imadazolidinyl, imidazolinyl, pyrazolidinyl, pyrazolinyl, piperidino, piperazinyl, indolinyl, isoindolinyl, isothiazolinone, benzisothiazolinone or tetrahydroisoquinolinyl each of which is optionally substituted.
Preferred optional substituents on Z include sulpho, carboxy, halogen (preferably chloro) alkoxy (preferably C1-6-alkoxy) or alkyl ((preferably C1-6-alkyl) optionally substituted by hydroxy, carboxy or sulpho. Especially preferred optional substituents on Z are C1-4-alkyl, carboxy or sulpho.
It is especially preferred that Z is morpholino or pyrrolidinyl optionally substituted by C1-4-alkyl, carboxy or sulpho.
The mono-azo group represented by D contains one azo group (xe2x80x94Nxe2x95x90Nxe2x80x94). Preferably D is a group of the Formula (2): 
wherein:
Ar is optionally substituted aryl or optionally substituted heteroaryl; and
L is optionally substituted arylene.
Preferred groups represented by Ar contain up to 20, more preferably up to 15 and especially up to 12 carbon atoms.
When Ar is optionally substituted aryl it is preferably optionally substituted phenyl, optionally substituted naphthyl or optionally substituted indanyl.
When Ar is optionally substituted heteroaryl it is preferably optionally substituted pyrazolonyl, optionally substituted pyridonyl (especially optionally substituted hydroxypyridonyl), optionally substituted thiophenyl, optionally substituted thiazolyl or optionally substituted benzisothiazolyl.
Preferably Ar is optionally substituted phenyl or optionally substituted naphthyl.
Preferred optional substituents on Ar include halogen (especially F and Cl), nitro, cyano, xe2x80x94CF3, xe2x80x94OR2, xe2x80x94SR2, xe2x80x94NR3R4, xe2x80x94C(O)R5, xe2x80x94C(O)OR6, xe2x80x94SO2R7, xe2x80x94SOR8 or C1-6-alkyl optionally substituted by xe2x80x94OH, xe2x80x94SO3H, xe2x80x94COOH, xe2x80x94PO3H2, C1-4-alkoxy or hydroxy-C1-4-alkylene-oxy;
wherein:
R2 is H, C1-6-alkyl optionally substituted by xe2x80x94OH, xe2x80x94SO3H or xe2x80x94COOH, or phenyl optionally substituted by C1-4-alkyl, xe2x80x94OH, xe2x80x94SO3H, xe2x80x94COOH, xe2x80x94NH2 or xe2x80x94NO2;
R3 and R4 are each independently H, xe2x80x94CO(C1-6-alkyl), xe2x80x94CONH2, C1-6-alkyl optionally substituted by xe2x80x94OH, xe2x80x94SO3H or xe2x80x94COOH, or phenyl optionally substituted by C1-4-alkyl, xe2x80x94OH, xe2x80x94SO3H, xe2x80x94COOH, xe2x80x94NH2 or xe2x80x94NO2; or
R3 and R4 together with the nitrogen to which they are attached form a 5- or 6-membered ring (preferably morpholine or piperazine); and
R6, R7, R8 and R9 are each independently C1-6-alkyl or phenyl.
Especially preferred optional substituents on Ar include one or more of C1-4-alkyl, C1-4-alkoxy, xe2x80x94OH, xe2x80x94COOH, xe2x80x94PO3H2, xe2x80x94SO3H, nitro, xe2x80x94Cl, xe2x80x94F,xe2x80x94CF3, amino and xe2x80x94COOC1-4-alkyl.
Preferred examples of groups represented by Ar include 2-carboxyphenyl, 3,5-dicarboxyphenyl, 2-sulphophenyl, 3-sulphophenyl, 2-carboxy-4-sulphophenyl, 3,4-dimethyl-6-sulphophenyl, 4-amino-2-hydroxyphenyl, 4-carboxy-2-hydroxyphenyl, 1,5-disulphonaphth-2-yl, 1-sulphonaphth-2-yl, 3,6,8-trisulphonapth-2-yl, 8-hydroxy-2,4-disulphonaphth-1-yl, 1-amino-8-hydroxy-3,6-disulphonaphth-2-yl, 2-amino-8-hydroxy-6-sulphonaphth-1-yl, 2-amino-8-hydroxy-6-sulphonaphth-7-yl, 2-amino-8-hydroxy-3,6-sulphonaphth-1-yl or 6-sulpho-indan-5-yl.
Preferably L is optionally substituted phenylene or optionally substituted naphthylene. Preferred optional substituents on L are the preferred optional substituents as hereinbefore described in relation to Ar.
When L is optionally substituted phenylene it is preferably a group of the Formula (3): 
wherein:
G is sulpho, carboxy, optionally substituted alkyl, optionally substituted alkoxy, xe2x80x94CF3 or xe2x80x94PO3H2; and
n is 0 to 4.
Preferably G is xe2x80x94SO3H, xe2x80x94COOH, xe2x80x94CF3, optionally substituted C1-4-alkyl, optionally substituted C1-4-alkoxy or xe2x80x94PO3H2, more preferably xe2x80x94SO3H, xe2x80x94COOH or xe2x80x94CF3 and especially xe2x80x94SO3H. Preferred optional substituents on G are selected from xe2x80x94OH, xe2x80x94SO3H, xe2x80x94COOH and xe2x80x94NH2, more preferably xe2x80x94OH.
n is preferably 0, 1 or 2, more preferably 1 or 2 and especially 1.
It is especially preferred that when L is of the Formula (3) it is a 1,4-phenylene group optionally carrying a substituent represented by G at the ortho position relative to the azo group in Formula (2).
When L is optionally substituted naphthylene it is preferably of the Formula (4): 
wherein:
G is as hereinbefore defined; and
q is 0 to 4.
Preferably q is 1 to 4. Preferably the group of Formula (4) carries at least one, more preferably two sulpho group(s). It is especially preferred that the compound of Formula (4) is of the Formula (5): 
wherein:
t is 0 or 1.
When t is 1 in Formula (5) the sulpho group is preferably attached at the 4- or more preferably the 3-position in the naphthylene ring. Preferably the azo group is attached at the 7-position of the naphthylene ring in Formula (5).
In a preferred embodiment L is a naphthylene group, preferably a group of the Formula (5) as hereinbefore described.
It is especially preferred that the compound of Formula (1) is magenta in colour.
In view of the foregoing preferences the compound of Formula (1) is preferably a compound of the Formula (6) or a salt thereof: 
wherein:
Ar1 is optionally substituted phenyl or optionally substituted naphthyl;
Z1 is an optionally substituted nitrogen containing heterocyclic group which is attached to the triazine ring by a bond to a nitrogen atom in the heterocyclic group;
R2 is H or C1-4-alkyl optionally substituted by xe2x80x94OH, xe2x80x94COOH or xe2x80x94SO3H; and
t is 0 or 1.
Preferably Z1 is as hereinbefore defined for Z except the heterocyclic group is attached to the triazine ring in Formula (6) by a bond to a nitrogen atom in the heterocyclic group. More preferably Z1 is an optionally substituted 5 or 6 membered heterocyclic group. It is especially preferred that Z1 is free from primary or secondary amino groups. More especially Z1 is morpholino or pyrrolidinyl each of which is optionally substituted by C1-4-alkyl, carboxy or sulpho.
Preferred optional substituents on Ar1 are as hereinbefore defined in relation to Ar. It is especially preferred that Ar1 is phenyl or naphthyl each of which is optionally substituted by one or more of xe2x80x94OH, xe2x80x94SO3H, xe2x80x94COOH, xe2x80x94NH2, C1-4-alkyl, C1-4-alkoxy or nitro.
When t is 1 the floating sulpho group in Formula (1) is preferably attached at the 3- or 4-position in the napthylene ring. More preferably t is 1 and the floating sulpho group is attached at the 3-position.
The compounds of Formula (6) provide prints which exhibit a high light-fastness and good water-fastness when incorporated into inks for ink jet printing. The compounds of Formula (6) are also highly soluble which improves operability and reduces crusting and nozzle blockage when inks containing the compounds are used in an ink jet printer.
Compounds of the present invention Formula (1) are free from fibre reactive groups. The term fibre reactive group is well known in the art and is described for example in EP 0356014 A1. Fibre reactive groups are capable, under suitable conditions, of reacting with the hydroxyl groups present in cellulosic fibres or with the amino groups present in natural fibres to form a covalent linkage between the fibre and the dye. As examples of fibre reactive groups excluded from the compounds of Formula (1) there may be mentioned aliphatic sulphonyl groups which contain a sulphate ester group in beta-position to the sulphur atom, e.g. beta-sulphato-ethylsulphonyl groups, alpha, beta-unsaturated acyl radicals of aliphatic carboxylic acids, for example acrylic acid, alpha-chloro-acrylic acid, alpha-bromoacrylic acid, propiolic acid, maleic acid and mono- and dichloro maleic; also the acyl radicals of acids which contain a substituent which reacts with cellulose in the presence of an alkali, e.g. the radical of a halogenated aliphatic acid such as chloroacetic acid, beta-chloro and beta-bromopropionic acids and alpha, beta-dichloro- and dibromopropionic acids or radicals of vinylsulphonyl- or beta-chloroethylsulphonyl- or beta-sulphatoethyl-sulphonyl-endo-methylene cyclohexane carboxylic acids. Other examples of cellulose reactive groups are tetrafluorocyclobutyl carbonyl, trifluoro-cyclobutenyl carbonyl, tetrafluorocyclobutylethenyl carbonyl, trifluoro-cyclobutenylethenyl carbonyl; activated halogenated 1,3-dicyanobenzene radicals; and heterocyclic radicals which contain 1, 2 or 3 nitrogen atoms in the heterocyclic ring and at least one cellulose reactive substituent on a carbon atom of the ring.
The compounds of the invention may be in the free acid or salt form. Preferred salts are water-soluble, for example alkali metal salts, especially lithium, sodium and potassium salts, ammonium, substituted ammonium and mixed salts thereof. Preferred alkali metal salts are those with sodium or lithium. It is especially preferred that the compound is in the form of a mixed lithium sodium salt, because we have found that these salts provide prints which exhibit a high light-fastness when incorporated into an ink jet printing ink.
Preferred ammonium and substituted ammonium salts have cations of the formula +NV4 wherein each V independently is H or optionally substituted alkyl, or two groups represented by V are H or optionally substituted alkyl and the remaining two groups represented by V, together with the N atom to which they are attached, form a 5- or 6-membered ring (preferably a morpholinyl, pyridinyl or piperidinyl ring).
Preferably each V independently is H or C1-4-alkyl, more preferably H, CH3 or CH3CH2, especially H. Thus the cation is preferably ammonium (i.e. +NH4).
Examples of cations include +NH4, morpholinium, piperidinium, pyridinium, (CH3)3N+H, (CH3)2N+H2, H2N+(CH3)(CH2CH3),CH3N+H3, CH3CH2N+H3, H2N+(CH2CH3)2, CH3CH2CH2N+H3, CH3CH2CH2N+H3, (CH3)2CHN+H3, N+(CH3)4, N+(CH2CH3)4, N-methyl pyridinium, N,N-dimethyl piperidinium and N,N-dimethyl morpholinium.
The compounds may be converted into a salt using known techniques. For example, an alkali metal salt of a compound may be converted into a salt with ammonia or an amine by dissolving an alkali metal salt of the dye in water, acidifying with a mineral acid and adjusting the pH of the solution to pH 9 to 9.5 with ammonia or the amine and removing the alkali metal cations by dialysis.
The present invention covers all tautomeric forms of the dyes shown in this specification, for example the hydrazo tautomers.
The compounds of the invention may be prepared using conventional techniques for the preparation of azo dyes. For example a suitable method comprises hydrolysing a compound of the Formula (7): 
wherein D, Z and R1 are as hereinbefore defined.
The hydrolysis is preferably performed by heating the compound of Formula (7) in an aqueous medium. Preferably the hydrolysis is performed under alkaline conditions, more preferably a pH in the range 8 to 14. The temperature during hydrolysis is preferably from 30 to 95xc2x0 C., more preferably from 40 to 90xc2x0 C. The efficiency of the hydrolysis may be improved by using a suitable catalyst, for example in the presence of a catalytic quantity of 1,4-diazabicyclo[2.2.2]octane (DABCO).
After the condensation reaction the product may be isolated by precipitating the product as a salt from the reaction mixture for example by the addition of a suitable alkali metal salt, especially sodium chloride. Alternatively, the product may be isolated in its free acid form by acidifying the reaction mixture, preferably using a mineral acid, especially hydrochloric acid. Where the product precipitates as a solid it may be separated from the mixture by filtration.
Unwanted anions may be, and preferably are removed from the product of the above process by dialysis, osmosis, ultrafiltration or a combination thereof.
The product of the above process may be converted to a salt by conventional techniques as hereinbefore described.
The compound of the Formula (7) may be prepared by, for example:
(i) condensing a compound of the formula DNHR1 with an approximately molar equivalent of cyanuric chloride; and
(ii) condensing the product of stage (i) with a compound of the formula ZH;
wherein D, R1 and Z are as hereinbefore defined.
Preferably the condensation in stage (i) is performed at a temperature of 5xc2x0 C. or less. It is preferred that the pH during the condensation is maintained above 5.5, more preferably above pH 6.
The condensation in stage (ii) is preferably performed at room temperature (20-30xc2x0 C.). Preferably the pH during the condensation is maintained in the range of from pH 7 to 8.5.
The compound of the formula DNHR1 may be prepared using conventional techniques for the preparation of azo dyes. For example when D is of the hereinbefore Formula (2): 
the compound may be prepared, for example by diazotising a compound of the formula ArNH2 and coupling with a compound of the formula LNHR1 using conventional techniques.
The present invention also covers mixtures comprising two or more compounds of the Formula (1). Furthermore, the compounds of Formula (1) may be mixed with commercially available dyes, especially those listed in the Colour Index International, to adjust the shade or other properties as desired.
According to a second aspect of the present invention there is provided a composition comprising:
(a) one or more compound according to the first aspect of the present invention (especially a magenta coloured compound); and
(b) one or more water-soluble magenta dye other than a compound according to the first aspect of the invention.
The water-soluble magenta dye is preferably a xanthene dye, an azo or bis azo dye, more preferably an anionic azo or bis azo dye and especially an azo or bis azo dye which contains one or more groups selected from sulphonate, carboxylate and thiocarboxylate groups.
Preferred water-soluble magenta dyes include C.I. Acid Red 50, 52, 87, 91, 92, 95, 249 and 289; C.I. Direct Violet 106 and 107; compounds 100 to 107, 200 and 201 described on pages 8 and 9 of WO96/24636; compounds 1 to 24 shown described on cols. 4 to 10 in U.S. Pat. No. 5,542,970; compounds 1 to 55 described on pages 7 to 17 of EP-A-682 088; compounds 1 to 14 shown in Example 1 to 6 of EP-A-194,885; compounds 1 to 24 described on pages 8 to 13 of EP-A-717 089; the compounds described in examples 1 to 16 in cols. 5 to 11 of U.S. Pat. No. 5,262,527; and the dyes described in Examples 1 to 21 in WO 94/16021.
Especially preferred water-soluble magenta dyes for use in the composition according to the second aspect of the invention include C.I. Acid Red 52, C.I. Acid Red 289 or a dye of the Formula (8), (9) and (10) and salts thereof: 
The dye of Formula (8) may be prepared using the method described in Example 1 of EP 0 559 310. The dye of the Formula (9) may be prepared using the method described in Example 3 of PCT publication number WO 94/16021. The dye of Formula (10) may be prepared using the method described in Example 1 of WO 96/24636.
The composition according to the second aspect of the present invention preferably comprises:
(a) from 1 to 99, more preferably from 3 to 70 and especially from 5 to 50 parts in total of the compound(s) according to the first aspect of the invention; and
(b) from 99 to 1, more preferably from 30 to 97 parts and especially 95 to 50 parts in total of the water-soluble magenta dye(s);
wherein the parts are by weight and the sum of the parts (a)+(b)=100.
The composition may contain a single dye of Formula (1) or a mixture thereof. Similarly, the composition may contain a single water-soluble magenta dye or a mixture of two or more water-soluble magenta dyes.
The compounds and compositions according to the first and second aspects of the present invention may be, and preferably are, purified to remove undesirable impurities before they are incorporated into inks for ink jet printing. Conventional techniques may be employed for purification, for example ultrafiltration, reverse osmosis and/or dialysis.
According to a third aspect of the present invention there is provided an ink comprising:
(a) a compound according to the first aspect of the present invention, or a composition according to the second aspect of the invention; and
(b) a liquid medium.
Preferably component (a) of the ink is one of the preferred compounds or compositions as hereinbefore described in relation to the first or second aspect of the invention. More preferably component (a) is one or more compounds of the Formula (1) or Formula (6) or salts thereof, as hereinbefore defined.
The liquid medium preferably comprises:
(i) water;
(ii) a mixture of water and an organic solvent; or
(iii) an organic solvent free from water.
The number of parts by weight of component (a) of the ink is preferably from 0.01 to 30, more preferably 0.1 to 20, especially from 0.5 to 15, and more especially from 1 to 5 parts. The number of parts by weight of component (b) is preferably from 99.99 to 70, more preferably from 99.9 to 80, especially from 99.5 to 85,and more especially from 99 to 95 parts. The number of parts (a)+(b) is 100.
Preferably component (a) is completely dissolved in component (b). Preferably component (a) has a solubility in component (b) at 20xc2x0 C. of at least 10%. This allows the preparation of concentrates which may be used to prepare more dilute inks and reduces the chance of the compound(s) of component (a) of the ink precipitating if evaporation of the liquid medium occurs during storage.
When the liquid medium comprises a mixture of water and an organic solvent, the weight ratio of water to organic solvent is preferably from 99:1 to 1:99, more preferably from 99:1 to 50:50 and especially from 95:5 to 80:20.
It is preferred that the organic solvent present in the mixture of water and organic solvent is a water-miscible organic solvent or a mixture of such solvents. Preferred water-miscible organic solvents include C1-6-alkanols, preferably methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, n-pentanol, cyclopentanol and cyclohexanol; linear amides, preferably dimethylformamide or dimethylacetamide; ketones and ketone-alcohols, preferably acetone, methyl ether ketone, cyclohexanone and diacetone alcohol; water-miscible ethers, preferably tetrahydrofuran and dioxane; diols, preferably diols having from 2 to 12 carbon atoms, for example pentane-1,5-diol, ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol and thiodiglycol and oligo- and poly-alkyleneglycols, preferably diethylene glycol, triethylene glycol, polyethylene glycol and polypropylene glycol; triols, preferably glycerol and 1,2,6-hexanetriol; mono-C1-4-alkyl ethers of diols, preferably mono-C1-4-alkyl ethers of diols having 2 to 12 carbon atoms, especially 2-methoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)-ethanol, 2-[2-(2-methoxyethoxy)ethoxy]ethanol, 2-[2-(2-ethoxyethoxy)-ethoxy]-ethanol and ethyleneglycol monoallylether; cyclic amides, preferably 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, caprolactam and 1,3-dimethylimidazolidone; cyclic esters, preferably caprolactone; sulphoxides, preferably dimethyl sulphoxide and sulpholane. Preferably the liquid medium comprises water and 2 or more, especially from 2 to 8, water-miscible organic solvents.
Examples of further suitable ink media comprising a mixture of water and one or more organic solvents are described in U.S. Pat. No. 4,963,189, U.S. Pat. No. 4,703,113, U.S. Pat. No. 4,626,284, EP 425,150A and U.S. Pat. No. 5,207,824.
When the liquid medium comprises an organic solvent free from water, (i.e. less than 1% water by weight) the solvent preferably has a boiling point of from 30xc2x0 to 200xc2x0 C., more preferably of from 40xc2x0 to 150xc2x0 C., especially from 50 to 125xc2x0 C. The organic solvent may be water-immiscible, water-miscible or a mixture of such solvents. Preferred water-miscible organic solvents are any of the hereinbefore described water-miscible organic solvents and mixtures thereof. Preferred water-immiscible solvents include, for example, aliphatic hydrocarbons; esters, preferably ethyl acetate; chlorinated hydrocarbons, preferably CH2Cl2; and ethers, preferably diethyl ether; and mixtures thereof.
When the liquid medium comprises a water-immiscible organic solvent, preferably a polar solvent is included because this enhances solubility of the dye in the liquid medium. Examples of polar solvents include C1-4-alcohols. In view of the foregoing preferences it is especially preferred that where the liquid medium is an organic solvent free from water it comprises a ketone (especially methyl ethyl ketone) and/or an alcohol (especially a C1-4-alkanol, such as ethanol or propanol).
The organic solvent free from water may be a single organic solvent or a mixture of two or more organic solvents. It is preferred that when the medium is an organic solvent free from water it is a mixture of 2 to 5 different organic solvents. This allows a medium to be selected which gives good control over the drying characteristics and storage stability of the ink.
Ink media comprising an organic solvent free from water are particularly useful where fast drying times are required and particularly when printing onto hydrophobic and non-absorbent substrates, for example plastics, metal and glass.
An especially preferred ink comprises:
(a) from 1 to 10 parts in total of a compound or composition according to the first or second aspect of the invention;
(b) from 2 to 60, more preferably 5 to 40 parts of water-soluble organic solvent; and
(c) from 30 to 97, more preferably 40 to 85 parts water;
wherein all parts are by weight and the sum of the parts (a)+(b)+(c)=100.
When the liquid medium in the ink comprises a mixture of water and an organic solvent; or an organic solvent free from water, component (a) of the ink may comprise a compound of the Formula (A) as hereinbefore defined in relation to the first aspect of the invention.
The inks according to the present invention may also contain additional components conventionally used in ink jet printing inks, for example viscosity and surface tension modifiers, corrosion inhibitors, biocides, kogation reducing additives, anti-cockle agents to reduce paper curling and surfactants which may be ionic or non-ionic.
The pH of the ink is preferably from 4 to 11, more preferably from 7 to 10.
The viscosity of the ink at 25xc2x0 C. is preferably less than 50 cP, more preferably less than 20 cP and especially less than 5 cP.
When the inks according to the invention are used as ink jet printing inks, the ink preferably has a concentration of less than 500 parts per million, more preferably less than 100 parts per million of halide ions. It is especially preferred that the ink has less than 100, more preferably less than 50 parts per million of divalent and trivalent metals, wherein parts refer to parts by weight relative to the total weight of the ink. We have found that purifying the inks to reduce the concentration of these undesirable ions reduces nozzle blockage in ink jet printing heads, particularly in thermal ink jet printers.
A fourth aspect of the present invention provides a process for printing an image on a substrate comprising applying thereto by means of an ink jet printer an ink containing a compound according to the first aspect of the invention, a composition according to the second aspect of the invention or a compound of the Formula (A) as hereinbefore defined in relation to the first aspect of the invention.
The ink used in this process is preferably as defined in the third aspect of the present invention.
The ink jet printer preferably applies the ink to the substrate in the form of droplets which are ejected through a small orifice onto the substrate. Preferred ink jet printers are piezoelectric ink jet printers and thermal ink jet printers. In thermal ink jet printers, programmed pulses of heat are applied to the ink in a reservoir by means of a resistor adjacent to the orifice, thereby causing the ink to be ejected in the form of small droplets directed towards the substrate during relative movement between the substrate and the orifice. In piezoelectric ink jet printers the oscillation of a small crystal causes ejection of the ink from the orifice.
The substrate is preferably paper, plastic, a textile, metal or glass, more preferably paper, an overhead projector slide or a textile material, especially paper.
Preferred papers are plain or treated papers which may have an acid, alkaline or neutral character. Examples of commercially available papers include, HP Premium Coated Paper, HP Photopaper (all available from Hewlett Packard Inc.), Stylus Pro 720 dpi Coated Paper, Epson Photo Quality Glossy Film, Epson Photo Quality Glossy Paper (available from Seiko Epson Corp.), Canon HR 101 High Resolution Paper, Canon GP 201 Glossy Paper, Canon HG 101 High Gloss Film (all available from Canon Inc.), Wiggins Conqueror paper (available from Wiggins Teape Ltd), Xerox Acid Paper and Xerox Alkaline paper, Xerox Acid Paper (available from Xerox).
A fifth aspect of the present invention provides a substrate, preferably a paper, an overhead projector slide or a textile material, printed with an ink according to the third aspect of the present invention or by means of the process according to the fourth aspect of the present invention.
According to a sixth aspect of the present invention there is provided an ink jet printer cartridge comprising a chamber and ink, wherein the ink is present in the chamber and the ink contains a compound or a composition according to the first or second aspect of the invention. Preferably the ink is an ink according to the third aspect of the invention.
According to an eighth aspect of the present invention there is provided an ink jet printer containing an ink jet printer cartridge, wherein the ink jet printer cartridge is as defined in the seventh aspect of the present invention.